Work robot system

ABSTRACT

A work robot system including a conveying apparatus that conveys an object, a robot that performs a predetermined task on a target portion of the object being conveyed by the conveying apparatus, a controller that controls the robot, a sensor that is attached to the robot and successively detects a position, relative to the robot, of the target portion of the object being conveyed by the conveying apparatus, and a force detector that detects a force generated by a contact between the object and a part supported by the robot. When the robot is performing the predetermined task, the controller performs force control based on a detection value of the force detector while controlling the robot by using a detection result of the sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority to Japanese PatentApplication No. 2018-021181 filed on Feb. 8, 2018, the entire content ofwhich is incorporated herein by reference.

FIELD

The present invention relates to a work robot system.

BACKGROUND

It has been often the case that, to attach a part to an object conveyedby a conveying apparatus, the conveying apparatus is stopped. Inparticular, to attach a part to a large object, such as a vehicle body,with precision, the transfer of the object by the conveying apparatusneeds to be stopped. In some cases, this results in deterioration of theworking efficiency.

On the other hand, a production line including a robot, a conveyingapparatus that conveys an object, rails provided along the conveyingapparatus, and a moving device that moves the robot along the rails, isknown (e.g., see Japanese Unexamined Patent Application, Publication No.H08-72764). In this production line, the robot performs a defectinspection and polishing on the object while the object is conveyed bythe conveying apparatus. Moreover, while the defect inspection andpolishing are performed, the moving device moves the robot along therails at the same speed as a speed at which the object is conveyed bythe conveying apparatus.

SUMMARY

A work robot system of an aspect of the present invention includes: aconveying apparatus that conveys an object; a robot that performs apredetermined task on a target portion of the object being conveyed bythe conveying apparatus; a controller that controls the robot; a sensorthat is attached to the robot and detects a position, relative to therobot, of the target portion of the object being conveyed by theconveying apparatus; and a force detector that detects a force generatedby contact between the object and a part or a tool supported by therobot, wherein when the robot is performing the predetermined task, thecontroller performs force control based on a detection value of theforce detector while controlling the robot by using a detection resultof the sensor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a work robot system of anembodiment of the present invention.

FIG. 2 is a block diagram of a control apparatus of the work robotsystem of the embodiment;

FIG. 3 is an example of image data captured by a detection apparatus ofthe work robot system of the embodiment.

FIG. 4 is a flowchart showing operations of a controller of the workrobot system of the embodiment.

FIG. 5 is a diagram illustrating calculation of an amount of movement inthe work robot system of the embodiment.

DETAILED DESCRIPTION

A work robot system 1 according to an embodiment of the presentinvention will be described below by using the drawings.

As shown in FIG. 1, the work robot system 1 of this embodiment includes:a conveying apparatus 2 that conveys an object 100 that is an object tobe worked on; a robot 10 that performs predetermined task on targetportions 101 of the object 100 being conveyed by the conveying apparatus2; a control apparatus 20 that controls the robot 10; a detectionapparatus 40 as a detector; and a sensor 50 mounted on the robot 10.

The detection apparatus 40 detects that the object 100 has been conveyedto a predetermined position. The detection apparatus 40 may acquire databy which positions and orientations of the target portions 101 of theobject 100 being conveyed by the conveying apparatus 2 can be specified.Any device that has this function can be used as the detection apparatus40. In this embodiment, the detection apparatus 40 is a photoelectricsensor. In this case, the detection apparatus 40 detects that the object100 has been conveyed to a position at which the detection apparatus 40is installed.

While the object 100 is not limited to a specific type of object, inthis embodiment, for example, the object 100 is a vehicle body. Theconveying apparatus 2 conveys the object 100 by driving some of aplurality of rollers 3 by means of a motor 2 a, and in this embodiment,the conveying apparatus 2 conveys the object 100 toward the right sidein FIG. 1. The motor 2 a may include an operating position detectiondevice 2 b. The operating position detection device 2 b successivelydetects a rotation position and a rotation amount of an output shaft ofthe motor 2 a. For example, the operating position detection device 2 bis an encoder. A detection value of the operating position detectiondevice 2 b is transmitted to the control apparatus 20.

The target portions 101 are portions of the object 100 on which therobot 10 performs the predetermined task. In this embodiment, as thepredetermined task, a hand 30 of the robot 10 lifts up a part 110 andthe robot 10 attaches attachment portions 111 of the part 110 onto thetarget portions 101. Thus, for example, shafts 111 a extending downwardfrom the attachment portions 111 of the part 110 are fitted into holes101 a provided in the target portions 101 of the object 100.

The robot 10 attaches the attachment portions 111 of the part 110 ontothe target portions 101 in a state where the object 100 is being movedby the conveying apparatus 2.

While the robot 10 is not limited to a specific type, the robot 10 ofthis embodiment includes a plurality of servomotors 11 that respectivelydrive a plurality of movable parts (see FIG. 2). Each servomotor 11 hasan operating position detection device that detects an operatingposition of the servomotor 11, and for example, this operating positiondetection device is an encoder. Detection values of the operatingposition detection devices are transmitted to the control apparatus 20.

The hand 30 is mounted at a distal end of the robot 10. The hand 30 ofthis embodiment supports the part 110 by grasping the part 110 with aplurality of claws, but a hand that supports the part 110 by using amagnetic force, air suction, or other means can also be used.

The hand 30 includes a servomotor 31 that drives the claws (see FIG. 2).The servomotor 31 has an operating position detection device thatdetects an operating position of the servomotor 31, and for example,this operating position detection device is an encoder. A detectionvalue of the operating position detection device is transmitted to thecontrol apparatus 20.

As the servomotors 11, 31, various types of servomotors, including arotary motor and a linear motor, can be used.

A force sensor 32 is mounted at the distal end portion of the robot 10.For example, the force sensor 32 detects forces in directions along anX-axis, a Y-axis, and a Z-axis shown in FIG. 3 and forces around theX-axis, the Y-axis, and the Z-axis. The force sensor 32 may be anysensor that can detect the direction and the magnitude of a forceapplied to the hand 30 or the part 110 grasped by the hand 30. For thispurpose, the force sensor 32 is provided between the robot 10 and thehand 30 in this embodiment, but the force sensor 32 may instead beprovided inside the hand 30.

The sensor 50 is mounted at the distal end side of the robot 10. In oneexample, the sensor 50 is mounted on a wrist flange of the robot 10together with the hand 30. The sensor 50 is a two-dimensional camera, athree-dimensional camera, a three-dimensional distance sensor, or thelike. The sensor 50 of this embodiment is a two-dimensional camera, andthe sensor 50 is a sensor that successively acquires image data of thetarget portions 101 as shown in FIG. 3, in a state where the targetportions 101 are located within a predetermined range of an angle ofview. The sensor 50 successively transmits the image data to the controlapparatus 20. The image data is data by which the position of at leastone of the two target portions 101 can be specified. It is also possibleto specify the orientations of the target portions 101, for example,based on the positional relationship between the two target portions 101in the image data.

Positions and directions of a coordinate system of the sensor 50 andpositions and directions of a coordinate system of the robot 10 areassociated with each other in advance in the control apparatus 20. Forexample, the coordinate system of the sensor 50 is set as a referencecoordinate system of the robot 10 that operates based on an operationprogram 23 b. Relative to this reference coordinate system, a coordinatesystem having the origin at a tool center point (TCP) of the hand 30, acoordinate system having the origin at a reference position of the part110, or the like, are represented.

As shown in FIG. 2, the control apparatus 20 includes: a controller 21having a CPU, an RAM, etc.; a display device 22; a storage unit 23having a non-volatile storage, an ROM, etc.; a plurality of servocontrollers 24 respectively corresponding to the servomotors 11 of therobot 10; a servo controller 25 corresponding to the servomotor 31 ofthe hand 30; and an input unit 26 connected to the control apparatus 20.In one example, the input unit 26 is an input device, such as aoperation panel, that an operator can carry. In some cases, the inputunit 26 wirelessly communicates with the control apparatus 20.

A system program 23 a is stored in the storage unit 23, and the systemprogram 23 a covers basic functions of the control apparatus 20. Theoperation program 23 b is also stored in the storage unit 23. Inaddition, a following control program 23 c and a force control program23 d are stored in the storage unit 23.

Based on these programs, the controller 21 transmits control commandsfor performing the predetermined task on the object 100 to the servocontrollers 24, 25. Accordingly, the robot 10 and the hand 30 performthe predetermined task on the object 100. Actions of the controller 21in this process will be described with reference to the flowchart ofFIG. 4.

First, when the object 100 has been detected by the detection apparatus40 (step S1-1), the controller 21 starts transmitting control commandsto the robot 10 and the hand 30 based on the operation program 23 b(step S1-2). Accordingly, the object 110 is grasped by the hand 30, andthe robot 10 brings the shafts 111 a of the part 110 grasped by the hand30 closer to the holes 101 a of the target portions 101. In this case,the controller 21 may use data such as the transfer speed of theconveying apparatus 2 or the positions of the target portions 101 of theobject 100, but does not need to use such data if the amount of transferby the conveying apparatus 2 is within the range of the field of view ofthe sensor 50. After step S1-7 to be described later, the shafts 111 aof the part 110 are fitted into the holes 101 a of the object 100 basedon the operation program 23 b.

As a result of the control of the robot 10 in step S1-2, for example,the part 110 reaches the position and orientation for fitting as shownin FIG. 1. When the target portions 101 have thus become present withinthe angle of view of the sensor 50 (step S1-3), the controller 21 startscontrol based on the following control program 23 c (step S1-4). Forexample, the following two modes of control can be used as this control.In the following two modes of control, the sensor 50 detects at leastthe positions of the target portions 101, and based on the detectedpositions, the controller 21 causes the distal end of the robot 10 tofollow the target portions 101.

The first one is a mode of control in which the controller 21 causes thedistal end of the robot 10 to follow the target portions 101, byconstantly disposing a characteristic shape and/or a characteristicpoint of the object 100 at a predetermined position in the angle of viewof the sensor 50. The second one is a mode of control in which thecontroller 21 causes the distal end of the robot 10 to follow the targetportions 101, by detecting the actual position (the actual positionrelative to the robot 10) of the characteristic shape and/or thecharacteristic point of the object 100, and correcting the operationprogram 23 b based on the difference between the position of thecharacteristic shape and/or the characteristic point and the actualposition.

In the first mode of control, the controller 21 detects thecharacteristic shape and/or the characteristic point in the image datathat is successively obtained by the sensor 50. The characteristic shaperefers to the shape of the entire target portion 101, the shape of thehole 101 a of the target portion 101, the shape of a mark M (FIG. 3)provided at the target portion 101, or the like. The characteristicpoint refers to a point indicating the position of the center of gravityof the hole 101 a of the target portion 101, a point indicating theposition of the center of gravity of the mark M provided at the targetportion 101, or the like. When the distance between the sensor 50 andthe target portion 101 in the Z-direction (the direction of viewing)changes, the characteristic shape changes in size while thecharacteristic point changes only a little or remains the same.

Then, using the image data successively obtained by the sensor 50, thecontroller 21 transmits, to the servo controller 24, control commandsfor constantly disposing the detected characteristic shape and/orcharacteristic point at the predetermined position in the image data.

In this case, it is preferable that the controller 21 use acharacteristic shape and/or a characteristic point that is visible tothe sensor 50 while the fitting work is performed, rather than acharacteristic shape and/or a characteristic point that is invisible tothe sensor 50 while the fitting work is performed. Alternatively, thecontroller 21 can change the characteristic shape and/or thecharacteristic point to be used for the following control, when thischaracteristic shape and/or characteristic point to be used for thefollowing control becomes invisible to the sensor 50.

In the second mode of control, using the image data successivelyobtained by the sensor 50, the controller 21 detects the actual positionof the characteristic shape and/or the characteristic point of theobject 100 relative to a fixed coordinate system of the robot 10. Then,the controller 21 corrects teaching points of the operation program 23 bwhich are taught with reference to the fixed coordinate system, based onthe difference between the position of the characteristic shape and/orthe characteristic point and the actual position.

In the first mode of control, the controller 21 may further calculatethe amount of movement of the target portions 101. In this case, thecontroller 21 causes the distal end of the robot 10 to follow the targetportions 101 by using also the calculated amount of movement.

The amount of movement of the target portions 101 is successivelycalculated, for example, based on the image data acquired by the sensor50. The amount of movement of the target portions 101 is calculated, forexample, by using the characteristic shape and/or the characteristicpoint appearing within the angle of view of the sensor 50.

The controller 21 conducts a matching process for matchingcharacteristic points in a plurality of consecutive pieces of imagedata. Since the distal end of the robot 10 moves in the same directionas the object 100 in accordance with the operation program 23 b, theposition of the characteristic point changes little in the plurality ofconsecutive pieces of image data. However, when the transfer speed ofthe conveying apparatus 2 and the moving speed of the distal end of therobot 10 are not exactly equal, the distal end of the robot 10 and theobject 100 move relative to each other. This relative movement iscaptured in the plurality of consecutive pieces of image data. Moreover,the amount of movement of the target portions 101 is successivelycalculated by using the moving speed of the distal end of the robot 10and the relative speed of the distal end of the robot 10 relative to thetarget portions 101.

The moving speed of the distal end of the robot 10 is a moving speedbased on the control commands from the controller 21. On the other hand,the moving speed of the distal end of the robot 10 relative to thetarget portions 101 is calculated based on the amount of movement of thecharacteristic shape and/or the characteristic point in the image dataand the time taken for the movement. As shown in FIG. 5, when positionsp11, p21, p31 of three characteristic shapes move respectively topositions p12, p22, p32, positions p13, p23, p33, and so on, the movingspeed of each of the three characteristic shapes is calculated byfitting based on the least-squares method or the like. Alternatively, anaverage moving speed is calculated by averaging the moving speeds of thethree characteristic shapes.

In the case where the amount of movement is calculated, even when thecharacteristic shape and/or the characteristic point used for thefollowing control becomes invisible to the sensor 50, the controller 21can cause the distal end of the robot 10 to follow the target portions101 by using the amount of movement that has been calculated before thecharacteristic shape and/or the characteristic point becomes invisible.

In the second mode of control, the controller 21 may further interpolatethe detection results of the actual positions of the characteristicshape and/or the characteristic point, for example, by using a trend ofthe calculated amount of movement or a trend of the detection result ofthe actual position. The actual position of the characteristic shapeand/or the characteristic point is calculated based on image data thatis actually captured by the sensor 50. Therefore, the acquisition cycleof the actual position is as long as the capturing cycle of the sensor50. However, by interpolating the detection results, it is possible, forexample, to detect or estimate the actual position during theacquisition cycle, or to estimate the actual position at a futuremoment.

By the above controls, the controller 21 causes the distal end of therobot 10 to follow the target portions 101. As a result, the targetportions 101 are disposed at predetermined positions in the captureddata acquired by the sensor 50. In this case, for example, the positionsin a horizontal direction of the shafts 111 a of the attachment portions111 of the part 110 and the positions in the horizontal direction of theholes 101 a of the target portions 101 coincide with each other.

Here, as described above, the coordinate system of the sensor 50 is setas the reference coordinate system of the robot 10 that is operatedbased on the operation program 23 b. Accordingly, the referencecoordinate system of the robot 10 moves in the conveying direction ofthe conveying apparatus 2, and the movement of the reference coordinatesystem coincides with the movement of the object 100 by the conveyingapparatus 2. In this situation, the target portions 101 of the object100 are being moved by the conveying apparatus 2, but when seen from thecontroller 21, the target portions 101 seem stationary in the referencecoordinate system.

In the state thus controlled, the controller 21 starts the force controlbased on the force control program 23 d (step S1-5). Publicly knownforce control can be used as the force control. In this embodiment, therobot 10 moves the part 110 in a direction away from a force detected bythe force sensor 32. The amount of this movement is determined by thecontroller 21 according to the detection value of the force sensor 32.

For example, when the shafts 111 a of the part 110 grasped by the hand30 and the holes 101 a of the object 100 start to fit, and in thissituation a force in the opposite direction from the conveying directionof the conveying apparatus 2 is detected by the force sensor 32, therobot 10 slightly moves the part 110 in the opposite direction from theconveying direction, away from the detected force, while following thetarget portions 101 in the reference coordinate system.

Subsequently, when the positions of the target portions 101 relative tothe robot 10 successively detected by the sensor 50 vary beyond apredetermined reference value (step S1-6), the controller 21 performs afirst abnormality addressing action (step S1-7). The variation beyondthe predetermined reference value is a significant movement of thetarget portion 101 in the image data, a movement at a speed higher thana predetermined speed of the target portion 101 in the image data, orthe like. When power supply is not stable, the rotation speed of themotor 2 a may decrease rapidly. Thus, the rotation speed of the motor 2a varies significantly in some cases. In such cases, the positions ofthe target portions 101 relative to the robot 10 vary beyond thepredetermined reference value.

As the first abnormality addressing action, the controller 21 performsan action of shortening the control cycle, enhancing the sensitivity ofthe force control, an action of stopping the progress of fitting, anaction of stopping the fitting work, etc. Shortening the control cycleor enhancing the sensitivity of the force control can cause the robot 10to move with higher responsiveness upon application of a force to thepart 110. In this embodiment, the controller 21 performs an action ofstopping the fitting work, an action of stopping the conveyingapparatus, or an action of a combination of these actions, etc.

When the detection value of the force sensor 32 exceeds a predeterminedreference value (step S1-8), the controller 21 performs a secondabnormality addressing action (step S1-9). When the detection value ofthe force sensor 32 exceeds the predetermined reference value, it ishighly likely that an abnormal force is applied to the part 110, theobject 100, etc. Therefore, as the second abnormality addressing action,the controller 21 performs an action of stopping the robot 10, an actionof moving the robot 10 at a low speed in a direction away from thedirection of the force detected by the force sensor 32, an action ofstopping the conveying apparatus, or an action of a combination of theseactions, etc. In this embodiment, the controller 21 performs an actionof stopping the robot 10.

On the other hand, the controller 21 determines whether the fitting workhas been completed (step S1-10), and when the fitting work has beencompleted, sends control commands to the robot 10 and the hand 30 (stepS1-11). Accordingly, the hand 30 moves away from the part 110, and thehand 30 is moved by the robot 10 to a stand-by position or a place wherea next part 110 is stocked.

Thus, in this embodiment, the position, relative to the distal end ofthe robot 10, of the target portions 101 of the object 100 beingconveyed by the conveying apparatus 2 are successively detected by thesensor 50 mounted on the robot 10, and the robot 10 is controlled byusing the detection result of the sensor 50. Therefore, even in theabsence of force control, the controller 21 may be able to recognize thepositional relationship between the object 100 and the part 110supported by the robot 10, and to recognize whether the two are incontact with each other. For example, the controller 21 can recognize,in the absence of force control, an abnormality of the conveyingapparatus 2 in which the amount the object 100 is moved by the conveyingapparatus 2 varies significantly. It is therefore possible to realizeprevention of damage to the robot 10, the conveying apparatus 2, theobject 100, etc. without unreasonably shortening the control cycle, orenhancing the sensitivity, of the force control, and also to suppressoscillation of the robot 10.

In this embodiment, the controller 21 performs the force control byusing the detection value of the force sensor 32, while causing the part110 supported by the robot 10 to follow the target portions 101 by usingthe detection result of the sensor 50.

Thus, the controller 21 causes the part 110 of the robot 10 to followthe target portions 101 by using the detection result of the sensor 50.In this way, when the robot 10 is performing the predetermined task, thecontroller 21 can accurately control the position and the orientation ofthe part 110 supported by the robot 10, relative to the target portions101 of the object 100 being conveyed by the conveying apparatus 2. Thisis advantageous in realizing prevention of damage to the robot 10, theconveying apparatus 2, the object 100, etc. without shortening thecontrol cycle, or enhancing the sensitivity, of the force control, andalso in suppressing oscillation of the robot 10.

In this embodiment, the detection apparatus 40 that detects at least thepositions of the target portions 101 of the object 100 on the conveyingapparatus 2 is provided, and the controller 21 brings the part 110supported by the robot 10 closer to the target portions 101 based on thedetection result of the detection apparatus 40. The work efficiency isimproved by the robot 10 thus operating based on the detection result ofthe detection apparatus 40. In this case, the controller 21 may also usethe detection result of the operating position detection device 2 b tobring the part 110 supported by the robot 10 closer to the targetportions 101. When the detection result of the operating positiondetection device 2 b is also used, the accuracy of the control ofbringing the part 110 closer to the target portions 101 is enhanced.

While the detection apparatus 40 is a photoelectric sensor in thisembodiment, the detection apparatus 40 may instead be, for example, atwo-dimensional camera, a three-dimensional camera, or athree-dimensional distance sensor that is disposed above, on a side of,or below the conveying apparatus 2, or a sensor that measures the shapeof an object by emitting linear light to the object. When the detectionapparatus 40 is a two-dimensional camera, the controller 21 may be ableto recognize the positions and the orientations of the target portions101 of the object 100 being conveyed by the conveying apparatus 2, basedon image data that is a detection result of the detection apparatus 40.Thus, the controller 21 can more accurately bring the shafts 111 a ofthe part 110 closer to the holes 101 a of the target portions 101 instep S1-2.

A processing tool may be supported at the distal end of the robot 10,and the robot 10 may perform processing as the predetermined task on theobject 100 being conveyed by the conveying apparatus 2. In this case,the processing tool refers to a drill, a milling cutter, a drill tap, adeburring tool, or other tools. Also in this case, effects similar tothose described above can be achieved as, for example, the processingtool is brought closer to the target portions 101 in step S1-2 and theforce control is performed according to contact between the processingtool and the target portions 101 in step S1-7.

In step S1-4, the controller 21 can also use the positions of the targetportions 101 in the image data, the moving speed and direction of thetarget portions 101 in the image data, etc. to cause the distal end ofthe robot 10 to follow the target portions 101. Other publicly knownmethods can also be used to cause the distal end of the robot 10 tofollow the target portions 101. Effects similar to those described abovecan be achieved also when such a configuration is used.

It is also possible to use, as the conveying apparatus 2, a conveyingapparatus that conveys the object 100 along a curvilinear route, or aconveying apparatus that conveys the object 100 along a winding route.In these cases, the controller 21 also can cause the distal end of therobot 10 to follow the target portions 101 by using the detection resultof the sensor 50. When the positions of the target portions 101 relativeto the robot 10 vary beyond the predetermined reference value in stepS1-6, the controller 21 can perform the first abnormality addressingaction in step S1-7. Thus, effects similar to those described above canbe achieved also when the above conveying means are used.

To acquire the amount of movement in step S1-4, the amount of movementis calculated based on the image data that is captured by the sensor 50in reality. Therefore, if the acquisition cycle of the amount ofmovement is matched with the capturing cycle of the sensor 50, theacquisition cycle of the amount of movement will become as long as thecapturing cycle of the sensor 50. However, it is also possible tointerpolate the amount of movement that is successively calculated basedon the data captured by the sensor 50. For example, the controller 21specifies a variation trend of the amount of movement by using acalculation result of a plurality of consecutive amounts of movement.Then, the controller 21 can set an interpolating amount of movementbetween one amount of movement and another along the specified trend.

In step S1-9, the controller 21 may perform, as the second abnormalityaddressing action, an action such as stopping the motor 2 a of theconveying apparatus 2 or decelerating the motor 2 a of the conveyingapparatus 2.

In this embodiment, the force sensor 32 is mounted at the distal end ofthe robot 10. However, it is also possible to dispose the force sensor32, for example, between the conveying apparatus 2 and the object 100 orinside the object 100. Also in this case, the force control based on thedetection value of the force sensor 32 can be performed, and effectssimilar to those described above can be thereby achieved.

The sensor 50 may be mounted at a part of the robot 10 other than thewrist flange. Also in this case, the controller 21 can recognize thepositional relationship between the part 110 supported by the robot 10and the object 100 being conveyed by the conveying apparatus 2 based onthe detection result of the sensor 50. Thus, effects similar to thosedescribed above can be achieved.

The following aspects are derived from the above disclosure.

A work robot system of an aspect of the present invention includes: aconveying apparatus that conveys an object; a robot that performs apredetermined task on a target portion of the object being conveyed bythe conveying apparatus; a controller that controls the robot; a sensorthat is attached to the robot and detects a position, relative to therobot, of the target portion of the object being conveyed by theconveying apparatus; and a force detector that detects a force generatedby contact between the object and a part or a tool supported by therobot, wherein when the robot is performing the predetermined task, thecontroller performs force control based on a detection value of theforce detector while controlling the robot by using a detection resultof the sensor.

In the above aspect, the position, relative to the robot, of the targetportion of the object being conveyed by the conveying apparatus isdetected by the sensor attached to the robot, and the robot iscontrolled by using the detection result of the sensor. Thus, even inthe absence of force control, the controller may be able to recognizethe positional relationship between the object and the part or the toolsupported by the robot, and to recognize whether the two are in contactwith each other. For example, the controller can recognize, in theabsence of force control, an abnormality of the conveying apparatus inwhich the moving amount the object moved by the conveying apparatusvaries significantly. It is therefore possible to realize prevention ofdamage to the robot, the conveying apparatus, the object, etc. withoutunreasonably shortening the control cycle of force control, and also tosuppress oscillation of the robot.

In the above aspect, preferably, the controller may perform the forcecontrol by using the detection value of the force detector, whilecausing the part or the tool supported by the robot to follow the targetportion by using the detection result of the sensor.

Thus, the controller causes the part or the tool of the robot to followthe target portion by using the detection result of the sensor. In thisway, when the robot is performing the predetermined task, the controllercan accurately control the position and the orientation of the part orthe tool supported by the robot, relative to the target portion of theobject being conveyed by the conveying apparatus. This is advantageousin realizing prevention of damage to the robot, the conveying apparatus,the object, etc. without shortening the control cycle, or enhancing thesensitivity, of the force control, and also in suppressing oscillationof the robot.

In the above aspect, preferably, the work robot system may furtherinclude a detector that detects at least a position of the targetportion of the object on the conveying apparatus, and the controller maybring the part or the tool of the robot closer to the target portionbased on a detection result of the detector.

This aspect is advantageous in accurately performing the control ofbringing the part or the tool supported by the robot closer to thetarget portion.

In the above aspect, preferably, at least one of the controller and theconveying apparatus may perform an abnormality addressing action whenthe position of the target portion relative to the robot detected by thesensor varies beyond a predetermined reference value.

According to this aspect, in the state where the positional relationshipbetween the object and the part or the tool supported by the robot isrecognized as described above, the controller further performs theabnormality addressing action based on the detection result of thesensor. This configuration is advantageous in reliably realizingprevention of damage to the robot, the conveying apparatus, the object,etc., and also in suppressing oscillation of the robot.

The above aspects can efficiently realize prevention of damage to therobot, the conveying apparatus, the object, etc.

REFERENCE SIGNS LIST

-   1 Work robot system-   2 Conveying apparatus-   2 a Motor-   2 b Operating position detection device-   3 Roller-   10 Robot-   11 Servomotor-   20 Control apparatus-   21 Controller-   22 Display device-   23 Storage unit-   23 a System program-   23 b Operation program-   23 c Following control program-   23 d Force control program-   24 Servo controller-   25 Servo controller-   26 Input unit-   30 Hand-   31 Servomotor-   32 Force sensor-   40 Detection apparatus-   50 Sensor-   100 Object-   101 Target portion-   101 a Hole-   110 Part-   111 Attachment portion-   111 a Shaft

1. A work robot system comprising: a conveying apparatus that conveys anobject; a robot that performs a predetermined task on a target portionof the object being conveyed by the conveying apparatus; a controllerthat controls the robot; a sensor that is attached to the robot anddetects a position, relative to the robot, of the target portion of theobject being conveyed by the conveying apparatus; and a force detectorthat detects a force generated by contact between the object and a partor a tool supported by the robot, wherein when the robot is performingthe predetermined task, the controller performs force control based on adetection value of the force detector while controlling the robot byusing a detection result of the sensor.
 2. The work robot systemaccording to claim 1, wherein the controller performs the force controlby using the detection value of the force detector, while causing thepart or the tool supported by the robot to follow the target portion byusing the detection result of the sensor.
 3. The work robot systemaccording to claim 2, further comprising a detector that detects atleast a position of the target portion of the object on the conveyingapparatus, wherein the controller brings the part or the tool of therobot closer to the target portion based on a detection result of thedetector.
 4. The work robot system according to claim 1, wherein atleast one of the controller and the conveying apparatus performs anabnormality addressing action when the position of the target portionrelative to the robot detected by the sensor varies beyond apredetermined reference value.